Hypercholesterolemia is known to be one of the prime risk factors for ischemic cardiovascular disease, such as arteriosclerosis. Bile acid sequestrants have been used to treat this condition; they seem to be moderately effective but they must be consumed in large quantities, i.e., several grams at a time and they are not very palatable.
MEVACOR.RTM. (lovastatin) and ZOCOR.RTM. (simavastatin), now commercially available, are members of a group of very active antihypercholesterolemic agents that function by limiting cholesterol biosynthesis by inhibiting the enzyme, HMG-CoA reductase.
Squalene synthetase is the enzyme involved in the first committed step of the de novo cholesterol biosynthetic pathway. This enzyme catalyzes the reductive dimerization of two molecules of farnesyl pyrophosphate to form squalene. The inhibition of this committed step to cholesterol should leave unhindered biosynthetic pathways to unbiquinone, dolichol and isopentenyl t-RNA.
Previous efforts at inhibiting squalene synthetase have employed pyrophosphate or pyrophosphate analogs containing compounds such as those described in P. Ortiz de Montellano et al, J. Med Chem. 20, 243 (1977) and E. J. Corey and R. Volante, J. Am. Chem. Soc., 98, 1291 (1976). S. Biller (U. S. Pat. No. 4, 871, 721) describes isoprenoid (phosphinylmethyl) phosphonates as inhibitors of squalene synthetase.
Recently certain nonphosphorous containing inhibitors of squalene synthetase have been isolated as natural products. These natural product inhibitors are described in U.S. Pat. Nos. 5,096,963 and 5,132,320 and 5,102,907. Semisynthetic analogs of these naturally ocurring compounds have been reported in EPO 512,865 publication. A need still remains for a more effective squalene synthetase inhibitors, i.e., one that provides a greater antihypercholesterolemic effect and exhibits a good safety profile.
The natural product inhibitors are tricarboxylic acids. The present applicants have now found that these natural products known as zaragozic acid A, zaragozic acid B and zaragozic acid C can be transformed following a photochemical conversion to the compounds of the present invention, which are potent cholesterol lowering agents.